Multilayer golf ball

ABSTRACT

A golf ball comprising a solid core, an outer cover layer, and a casing disposed between the core and the outer cover layer, wherein the core has an outer diameter of no greater than about 1.58 inches; the casing has an outer diameter of greater than 1.58 inches and a material hardness of between about 30 and about 70 Shore D; and the outer cover layer has a material hardness of less than about 45 Shore D.

FIELD OF THE INVENTION

[0001] This invention relates generally to golf balls, and morespecifically, to multilayer golf balls. In particular, this inventionrelates to a golf ball having a core and a cover comprising a thin innercover layer (a “casing”) and a soft, thin, outer cover layer.

BACKGROUND OF THE INVENTION

[0002] There are a variety of different types of golf ballconstructions, the majority of which, however, fall into two generalcategories: solid and wound golf balls. Solid golf balls includeone-piece, two-piece, and multi-layer golf balls. One-piece golf ballsare inexpensive and easy to construct, but have poor playingcharacteristics and are, therefore, usually limited for use as rangeballs. Two-piece balls are generally constructed with a polybutadienesolid core and a cover and are typically the most popular withrecreational golfers because they are very durable and provide gooddistance. These balls are also relatively inexpensive and easy tomanufacture, but are regarded by top players as having limited playingcharacteristics. Multi-layer golf balls are comprised of a solid coreand a cover, either of which may be formed of one or more layers. Theseballs are regarded as having an extended range of playingcharacteristics, but are more expensive and difficult to manufacturethan are one- and two-piece golf balls.

[0003] Wound golf balls, which typically include a fluid-filled centersurrounded by tensioned elastomeric material and a cover, generallyprovide higher spin and soft “feel” characteristics but are moredifficult and expensive to manufacture than are one-piece, two-piece,and multi-layer golf balls. Manufacturers are, therefore, constantlystriving to produce a solid ball that incorporates the beneficialcharacteristics of a wound construction.

[0004] A variety of golf balls have been designed by manufacturers toprovide a wide range of playing characteristics, such as compression,velocity, “feel,” and spin. These characteristics can be adjusted andoptimized for a variety of playing abilities. For example, manufacturerscan adjust these properties by altering the materials (i.e., polymercompositions) and/or the physical construction of each or all of thevarious golf ball components (i.e., centers, cores, intermediate layers,and covers). Polymers commonly employed by manufacturers for theconstruction of golf balls include polybutadiene (cores), ionomers, suchas SURLYN, commercially available from DuPont (covers and intermediatelayers), and polyurethanes (covers and intermediate layers). Finding theright combination of core and layer materials and construction toproduce a golf ball suited for a predetermined set of performancecriteria, in particular, increased resilience and, therefore, velocity,without a loss in “feel” is a task that is challenging.

[0005] It is desirable, therefore, to construct a ball having increasedresilience formed of a soft, thin, urethane cover layer combined with aharder, thin ionomer casing, according to the present invention. Thisconstruction, coupled with a high-Mooney-viscosity polybutadiene core,also described by the present invention, has been found to raise thevelocity of a golf ball prepared in this manner without detrimentallyaffecting desirable ball characteristics, such as spin, “feel,” andresiliency.

SUMMARY OF THE INVENTION

[0006] The present invention is directed to a golf ball comprising asolid core, an outer cover layer, and a casing disposed between the coreand the outer cover layer, wherein the core has an outer diameter of nogreater than about 1.58 inches; the casing has an outer diameter ofgreater than 1.58 inches and a material hardness of between about 30 andabout 70 Shore D; and the outer cover layer has a material hardness ofless than about 45 Shore D.

[0007] In one embodiment, the outer cover layer material hardness isless than about 40 Shore D and, alternatively, the outer cover layermaterial hardness is between about 25 and about 40 Shore D. The casingmaterial hardness is preferably between about 50 and about 65 Shore Dand, further, at least one of the casing and the outer cover layer has athickness of less than about 0.05 inches. It is preferred that at leastone of the casing and the outer cover layer has a thickness of betweenabout 0.02 inches and about 0.04 inches.

[0008] The casing outer diameter should be from about 1.58 inches toabout 1.64 inches and preferably, from about 1.59 inches to about 1.63inches. In another embodiment, the outer cover layer is formed of apolyurethane composition comprising the reaction product of at least onepolyisocyanate, a polyol, and at least one curing agent.

[0009] In another embodiment, the ball has a moment of inertia of lessthan about 85 g.cm² and, preferably, the ball has a moment of inertia ofless than about 83 g.cm². The core, alternatively, has a first hardnessand the casing has a second hardness greater than the first and/or theouter cover layer has a third hardness less than the second hardness.The casing comprises ionic copolymers of ethylene and an unsaturatedmonocarboxylic acid; thermoplastic and thermoset resins; metallocenes;vinyl resins; polyolefins; polyurethanes; polyureas; polyamides; acrylicresins; thermoplastic polyesters; and mixtures thereof. In a preferredembodiment, the casing comprises comprises ionic copolymers of ethyleneand an unsaturated monocarboxylic acid.

[0010] In still another embodiment, the casing material hardness isbetween about 40 and about 70 Shore D and the outer cover layer materialhardness is less than about 40 Shore D. Alternatively, a ratio of thecasing material hardness (Shore D) to the outer cover layer materialhardness is greater than 1.5.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a cross-sectional view of a golf ball having a core andan inner and outer cover according to the present invention.

DEFINITIONS

[0012] The term “about,” as used herein in connection with one or morenumbers or numerical ranges, should be understood to refer to all suchnumbers, including all numbers in a range.

[0013] As used herein, “cis-to-trans catalyst” means any component or acombination thereof that will convert at least a portion ofcis-polybutadiene isomer to trans-polybutadiene isomer at a giventemperature. It should be understood that the combination of thecis-isomer, the trans-isomer, and any vinyl-isomer, measured at anygiven time, comprises 100 percent of the polybutadiene.

[0014] As used herein, the term “active ingredients” is defined as thespecific components of a mixture or blend that are essential to thechemical reaction.

[0015] As used herein, substituted and unsubstituted “aryl” groups meansa hydrocarbon ring bearing a system of conjugated double bonds,typically comprising 4n+27π ring electrons, where n is an integer.Examples of aryl groups include, but are not limited to phenyl,naphthyl, anisyl, tolyl, xylenyl and the like. According to the presentinvention, aryl also includes heteroaryl groups, e.g., pyrimidine orthiophene. These aryl groups may also be substituted with any number ofa variety of functional groups. In addition to the functional groupsdescribed herein in connection with carbocyclic groups, functionalgroups on the aryl groups can include hydroxy and metal salts thereof;mercapto and metal salts thereof; halogen; amino, nitro, cyano, andamido; carboxyl including esters, acids, and metal salts thereof; silyl;acrylates and metal salts thereof; sulfonyl or sulfonamide; andphosphates and phosphites; and a combination thereof.

[0016] As used herein, the term “Atti compression” is defined as thedeflection of an object or material relative to the deflection of acalibrated spring, as measured with an Atti Compression Gauge, that iscommercially available from Atti Engineering Corp. of Union City, N.J.Atti compression is typically used to measure the compression of a golfball. When the Atti Gauge is used to measure cores having a diameter ofless than 1.680 inches, it should be understood that a metallic or othersuitable shim is used to make the diameter of the measured object 1.680inches.

[0017] As used herein, substituted and unsubstituted “carbocyclic” meanscyclic carbon-containing compounds, including, but not limited tocyclopentyl, cyclohexyl, cycloheptyl, adamantyl, and the like. Suchcyclic groups may also contain various substituents in which one or morehydrogen atoms has been replaced by a functional group. Such functionalgroups include those described above, and lower alkyl groups having from1-28 carbon atoms. The cyclic groups of the invention may furthercomprise a heteroatom.

[0018] As used herein, the term “coefficient of restitution” for golfballs is defined as the ratio of the rebound velocity to the inboundvelocity when balls are fired into a rigid plate with a mass of at least50 lb. The inbound velocity is understood to be 125 ft/s.

[0019] As used herein, the terms “Group VIA component” or “Group VIAelement” mean a component that includes a sulfur component, a seleniumcomponent, or a tellurium component, or a combination thereof.

[0020] As used herein, the term “sulfur component” means a componentthat is elemental sulfur, polymeric sulfur, or a combination thereof. Itshould be further understood that “elemental sulfur” refers to the ringstructure of S8 and that “polymeric sulfur” is a structure including atleast one additional sulfur relative to the elemental sulfur.

[0021] As used herein, the term “fluid” includes a liquid, a paste, agel, a gas, or any combination thereof.

[0022] As used herein, the term “molecular weight” is defined as theabsolute weight average molecular weight. The molecular weight isdetermined by the following method:

[0023] approximately 20 mg of polymer is dissolved in 10 mL oftetrahydrofuran (“THF”), which may take a few days at room temperaturedepending on the polymer's molecular weight and distribution. One literof THF is filtered and degassed before being placed in ahigh-performance liquid chromatography (“HPLC”) reservoir. The flow rateof the HPLC is set to 1 mL/min through a Viscogel column. Thisnon-shedding, mixed bed, column model GMHHR-H, which has an ID of 7.8 mmand 300 mm long is available from Viscotek Corp. of Houston, Tex. TheTHF flow rate is set to 1 mL/min for at least one hour before sampleanalysis is begun or until stable detector baselines are achieved.During this purging of the column and detector, the internal temperatureof the Viscotek TDA Model 300 triple detector should be set to 40° C.This detector is also available from Viscotek Corp. The three detectors(i.e., Refractive Index, Differential Pressure, and Light Scattering)and the column should be brought to thermal equilibrium, and thedetectors should be purged and zeroed, to prepare the system forcalibration according to the instructions provided with this equipment.A 100-μL aliquot of sample solution can then be injected into theequipment and the molecular weight of each sample can be calculated withthe Viscotek's triple detector software. When the molecular weight ofthe polybutadiene material is measured, a dn/dc of 0.130 should alwaysbe used. It should be understood that this equipment and these methodsprovide the molecular weight numbers described and claimed herein, andthat other equipment or methods will not necessarily provide equivalentvalues as used herein.

[0024] As used herein, the term “multilayer” means at least two layersand includes liquid center balls, wound balls, hollow-center balls, andballs with at least two intermediate layers and/or an inner and an outercover.

[0025] As used herein, the term “thermoset” material refers to anirreversible, solid polymer that is the product of the reaction of atleast one polymer and at least one crosslinking agent.

[0026] As used herein, the term “parts per hundred,” also known as“phr,” is defined as the number of parts by weight of a particularcomponent present in a mixture, relative to 100 parts by weight of thetotal polymer component. Mathematically, this can be expressed as theweight of an ingredient divided by the total weight of the polymer,multiplied by a factor of 100.

[0027] As used herein, the term “substantially free” means less thanabout 5 weight percent, preferably less than about 3 weight percent,more preferably less than about 1 weight percent, and most preferablyless than about 0.01 weight percent.

[0028] As used herein the term “resilience index” is defined as thedifference in loss tangent measured at 10 cpm and 1000 cpm divided by990 (the frequency span) multiplied by 100,000 (for normalization andunit convenience). The loss tangent is measured using an RPA 2000manufactured by Alpha Technologies of Akron, OH. The RPA 2000 is set tosweep from 2.5 to 1000 cpm at a temperature of 100° C. using an arc of0.5 degrees. An average of six loss tangent measurements are acquired ateach frequency and the average is used in calculation of the resilienceindex. The computation of resilience index is as follows:

Resilience Index=100,000·[(loss tangent @ 10 cpm)−(loss tangent @ 1000cpm)]/990

DETAILED DESCRIPTION OF THE INVENTION

[0029] Referring to FIG. 1, a golf ball 10 of the present inventionincludes a core 12, a casing 14 surrounding the core 12, and an outercover layer 16. The golf ball cores of the present invention maycomprise a variety of constructions. The core may be a single layer ormay comprise a plurality of layers. The core may also comprise a solidcenter around which many yards of a tensioned elastomeric material arewound.

[0030] The materials for solid cores include compositions having a baserubber, a crosslinking agent, a filler, and a co-crosslinking orinitiator agent. The base rubber typically includes natural or syntheticrubbers. A preferred base rubber is 1,4-polybutadiene having acis-structure of at least 40%. Most preferably, the base rubbercomprises high-Mooney-viscosity rubber. If desired, the polybutadienecan also be mixed with other elastomers known in the art such as naturalrubber, polyisoprene rubber and/or styrene-butadiene rubber in order tomodify the properties of the core.

[0031] The crosslinking agent includes a metal salt of an unsaturatedfatty acid such as a zinc salt or a magnesium salt of an unsaturatedfatty acid having 3 to 8 carbon atoms such as acrylic or methacrylicacid. Suitable cross linking agents include metal salt diacrylates,dimethacrylates and monomethacrylates wherein the metal is magnesium,calcium, zinc, aluminum, sodium, lithium or nickel.

[0032] The initiator agent can be any known polymerization initiatorwhich decomposes during the cure cycle. Suitable initiators includeperoxide compounds such as dicumyl peroxide, 1,1-di(t-butylperoxy)3,3,5-trimethyl cyclohexane, a-a bis (t-butylperoxy) diisopropylbenzene,2,5-dimethyl-2,5 di(t-butylperoxy) hexane or di-t-butyl peroxide andmixtures thereof.

[0033] As used herein, the term “filler” includes any compound orcomposition that can be used to vary the density and other properties ofthe core. Fillers typically include materials such as tungsten, zincoxide, barium sulfate, silica, calcium carbonate, zinc carbonate,metals, metal oxides and salts, regrind (recycled core materialtypically ground to about 30 mesh particle), high-Mooney-viscosityrubber regrind, and the like.

[0034] The invention also includes a method to convert the cis-isomer ofthe polybutadiene resilient polymer component to the trans-isomer duringa molding cycle and to form a golf ball. A variety of methods andmaterials have been disclosed in U.S. Pat. No. 6,162,135 and U.S.application Ser. No. 09/461,736, filed Dec. 16, 1999; Ser. No.09/458,676, filed Dec. 10, 1999; and Ser. No. 09/461,421, filed Dec. 16,1999, each of which are incorporated herein, in their entirety, byreference. Various combinations of polymers, cis-to-trans catalysts,fillers, crosslinkers, and a source of free radicals, may be used. Toobtain a higher resilience and lower compression center or intermediatelayer, a high-molecular weight polybutadiene with a cis-isomer contentpreferably greater than about 90 percent is converted to increase thepercentage of trans-isomer content at any point in the golf ball orportion thereof, preferably to increase the percentage throughoutsubstantially all of the golf ball or portion thereof, during themolding cycle. More preferably, the cis-polybutadiene isomer is presentin an amount of greater than about 95 percent of the total polybutadienecontent. Without wishing to be bound by any particular theory, it isbelieved that a low amount of 1,2-polybutadiene isomer(“vinyl-polybutadiene”) is desired in the initial polybutadiene, and thereaction product. Preferably, the vinyl polybutadiene isomer content isless than about 7 percent. More preferably, the vinyl polybutadieneisomer content is less than about 4 percent. Most preferably, the vinylpolybutadiene isomer content is less than about 2 percent. Withoutwishing to be bound by any particular theory, it is also believed thatthe resulting mobility of the combined cis- and trans-polybutadienebackbone is responsible for the lower modulus and higher resilience ofthe reaction product and golf balls including the same.

[0035] Crosslinkers are included to increase the hardness of thereaction product. Suitable crosslinking agents include one or moremetallic salts of unsaturated fatty acids or monocarboxylic acids, suchas zinc, calcium, or magnesium acrylate salts, and the like, andmixtures thereof. Preferred acrylates include zinc acrylate, zincdiacrylate, zinc methacrylate, and zinc dimethacrylate, and mixturesthereof. The crosslinking agent must be present in an amount sufficientto crosslink a portion of the chains of polymers in the resilientpolymer component. For example, the desired compression may be obtainedby adjusting the amount of crosslinking. This may be achieved, forexample, by altering the type and amount of crosslinking agent, a methodwell-known to those of ordinary skill in the art. The crosslinking agentis typically present in an amount greater than about 10 phr of thepolymer component, preferably from about 10 to 40 phr of the polymercomponent, more preferably from about 10 to 30 phr of the polymercomponent. When an organosulfur is selected as the cis-to-transcatalyst, zinc diacrylate may be selected as the crosslinking agent andis present in an amount of less than about 40 phr.

[0036] Fillers added to one or more portions of the golf ball typicallyinclude processing aids or compounds to affect rheological and mixingproperties, density-modifying fillers, tear strength, or reinforcementfillers, and the like. The fillers are generally inorganic, and suitablefillers include numerous metals or metal oxides, such as zinc oxide andtin oxide, as well as barium sulfate, zinc sulfate, calcium carbonate,barium carbonate, clay, tungsten, tungsten carbide, an array of silicas,and mixtures thereof. Fillers may also include various foaming agents orblowing agents which may be readily selected by one of ordinary skill inthe art. Fillers may include polymeric, ceramic, metal, and glassmicrospheres may be solid or hollow, and filled or unfilled. Fillers aretypically also added to one or more portions of the golf ball to modifythe density thereof to conform to uniform golf ball standards. Fillersmay also be used to modify the weight of the center or at least oneadditional layer for specialty balls, e.g., a lower weight ball ispreferred for a player having a low swing speed.

[0037] The polymers, free-radical initiator, filler(s), and any othermaterials used in forming either the golf ball center or any portion ofthe core, in accordance with the invention, may be combined to form amixture by any type of mixing known to one of ordinary skill in the art.Suitable types of mixing include single pass and multi-pass mixing, andthe like. The crosslinking agent, and any other optional additives usedto modify the characteristics of the golf ball center or additionallayer(s), may similarly be combined by any type of mixing. A single-passmixing process where ingredients are added sequentially is preferred, asthis type of mixing tends to increase efficiency and reduce costs forthe process. The preferred mixing cycle is single step wherein thepolymer, cis-to-trans catalyst, filler, zinc diacrylate, and peroxideare added sequentially. Suitable mixing equipment is well known to thoseof ordinary skill in the art, and such equipment may include a Banburymixer, a two-roll mill, or a twin screw extruder.

[0038] Conventional mixing speeds for combining polymers are typicallyused, although the speed must be high enough to impart substantiallyuniform dispersion of the constituents. On the other hand, the speedshould not be too high, as high mixing speeds tend to break down thepolymers being mixed and particularly may undesirably decrease themolecular weight of the polymer component. The speed should thus be lowenough to avoid high shear, which may result in loss of desirably highmolecular weight portions of the polymer component. Also, too high amixing speed may undesirably result in creation of enough heat toinitiate the during the mixing cycle. The mixing temperature dependsupon the type of polymer components, and more importantly, on the typeof free-radical initiator. For example, when usingdi(2-t-butyl-peroxyisopropyl)benzene as the free-radical initiator, amixing temperature of about 80° C. to 125° C., preferably about 88° C.to 110° C., and more preferably about 90° C. to 100° C., is suitable tosafely mix the ingredients. Additionally, it is important to maintain amixing temperature below the peroxide decomposition temperature. Forexample, if dicumyl peroxide is selected as the peroxide, thetemperature should not exceed 100° F. Suitable mixing speeds andtemperatures are well-known to those of ordinary skill in the art, ormay be readily determined without undue experimentation.

[0039] The mixture can be subjected to, e.g., a compression or injectionmolding process, to obtain solid spheres for the center or hemisphericalshells for forming an intermediate layer. The polymer mixture issubjected to a molding cycle in which heat and pressure are appliedwhile the mixture is confined within a mold. The cavity shape depends onthe portion of the golf ball being formed. The heat liberates freeradicals by decomposing one or more peroxides, which may initiate thecis-to-trans conversion and crosslinking simultaneously. The temperatureand duration of the molding cycle are selected based upon reactivity ofthe mixture. The molding cycle may have a single step of molding themixture at a single temperature for a fixed time duration. An example ofa single step molding cycle, for a mixture that contains dicumylperoxide, would hold the polymer mixture at 340° F. for a duration of 15minutes. The molding cycle may also include a two-step process, in whichthe polymer mixture is held in the mold at an initial temperature for aninitial duration of time, followed by holding at a second, typicallyhigher temperature for a second duration of time. An example of atwo-step molding cycle would be holding the mold at 290° F. for 40minutes, then ramping the mold to 340° F. where it is held for aduration of 20 minutes. In a preferred embodiment of the currentinvention, a single-step cure cycle is employed. Single-step processesare effective and efficient, reducing the time and cost of a two-stepprocess. The polybutadiene, cis-to-trans conversion catalyst, additionalpolymers, free-radical initiator, filler, and any other materials usedin forming either the golf ball center or any portion of the core, inaccordance with the invention, may be combined to form a golf ball by aninjection molding process, which is also well-known to one of ordinaryskill in the art. Although the curing time depends on the variousmaterials selected, a particularly suitable curing time is about 5 to 18minutes, preferably from about 8 to 15 minutes, and more preferably fromabout 10 to 12 minutes. Those of ordinary skill in the art will bereadily able to adjust the curing time upward or downward based on theparticular materials used and the discussion herein.

[0040] The crosslinked or cured polymer component, which contains agreater amount of trans-polybutadiene than the uncured polymercomponent, is formed into an article having a first hardness at a pointin the interior and a surface having a second hardness such that thesecond hardness differs from the first hardness by greater than 10percent of the first hardness. Preferably, the article is a sphere andthe first point is the midpoint of the article. In another embodiment,the second hardness differs from the first by greater than 20 percent ofthe first hardness. The cured article also has a first amount oftrans-polybutadiene at an interior location and a second amount oftrans-polybutadiene at a surface location, wherein the first amount isat least about 6 percent less than the second amount, preferably atleast about 10 percent less than the second amount, and more preferablyat least about 20 percent less than the second amount. The interiorlocation is preferably a midpoint and the article is preferably asphere. In one embodiment, the compression of the core, or portion ofthe core, of golf balls prepared according to the invention ispreferably below about 50, more preferably below about 25.

[0041] The cover provides the interface between the ball and a club.Properties that are desirable for the cover include good moldability,high abrasion resistance, high tear strength, high resilience, and goodmold release. The cover typically has a thickness to provide sufficientstrength, good performance characteristics, and durability. The coverpreferably has a thickness of less than about 0.1 inches, morepreferably, less than about 0.05 inches, and most preferably, betweenabout 0.02 inches and about 0.04 inches. The invention is particularlydirected towards a multilayer golf ball which comprises a core, acasing, and an outer cover layer. In this embodiment, preferably, atleast one of the casing and outer cover layer has a thickness of lessthan about 0.05 inches, more preferably between about 0.02 inches andabout 0.04 inches. Most preferably, the thickness of either layer isabout 0.03 inches.

[0042] When the golf ball of the present invention includes a casing,this layer can include any materials known to those of ordinary skill inthe art, including thermoplastic and thermosetting material, butpreferably the casing can include any suitable materials, such as ioniccopolymers of ethylene and an unsaturated monocarboxylic acid which areavailable under the trademark SURLYN of E.I. DuPont de Nemours & Co., ofWilmington, Del., or IOTEK or ESCOR of Exxon. These are copolymers orterpolymers of ethylene and methacrylic acid or acrylic acid partiallyneutralized with salts of zinc, sodium, lithium, magnesium, potassium,calcium, manganese, nickel or the like, in which the salts are thereaction product of an olefin having from 2 to 8 carbon atoms and anunsaturated monocarboxylic acid having 3 to 8 carbon atoms. Thecarboxylic acid groups of the copolymer may be totally or partiallyneutralized and might include methacrylic, crotonic, maleic, fumaric oritaconic acid.

[0043] This golf ball can likewise include one or more homopolymeric orcopolymeric casing materials, such as:

[0044] (1) Vinyl resins, such as those formed by the polymerization ofvinyl chloride, or by the copolymerization of vinyl chloride with vinylacetate, acrylic esters or vinylidene chloride;

[0045] (2) Polyolefins, such as polyethylene, polypropylene,polybutylene and copolymers such as ethylene methylacrylate, ethyleneethylacrylate, ethylene vinyl acetate, ethylene methacrylic or ethyleneacrylic acid or propylene acrylic acid and copolymers and homopolymersproduced using a single-site catalyst or a metallocene catalyst;

[0046] (3) Polyurethanes, such as those prepared from polyols anddiisocyanates or polyisocyanates and those disclosed in U.S. Pat. No.5,334,673;

[0047] (4) Polyureas, such as those disclosed in U.S. Pat. No.5,484,870;

[0048] (5) Polyamides, such as poly(hexamethylene adipamide) and othersprepared from diamines and dibasic acids, as well as those from aminoacids such as poly(caprolactam), and blends of polyamides with SURLYN,polyethylene, ethylene copolymers, ethyl-propylene-non-conjugated dieneterpolymer, and the like;

[0049] (6) Acrylic resins and blends of these resins with poly vinylchloride, elastomers, and the like;

[0050] (7) Thermoplastics, such as urethanes; olefinic thermoplasticrubbers, such as blends of polyolefins withethylene-propylene-non-conjugated diene terpolymer; block copolymers ofstyrene and butadiene, isoprene or ethylene-butylene rubber; orcopoly(ether-amide), such as PEBAX, sold by ELF Atochem of Philadelphia,Pa.;

[0051] (8) Polyphenylene oxide resins or blends of polyphenylene oxidewith high impact polystyrene as sold under the trademark NORYL byGeneral Electric Company of Pittsfield, Mass.;

[0052] (9) Thermoplastic polyesters, such as polyethylene terephthalate,polybutylene terephthalate, polyethylene terephthalate/glycol modifiedand elastomers sold under the trademarks HYTREL by E.I. DuPont deNemours & Co. of Wilmington, Del., and LOMOD by General Electric Companyof Pittsfield, Mass.;

[0053] (10) Blends and alloys, including polycarbonate withacrylonitrile butadiene styrene, polybutylene terephthalate,polyethylene terephthalate, styrene maleic anhydride, polyethylene,elastomers, and the like, and polyvinyl chloride with acrylonitrilebutadiene styrene or ethylene vinyl acetate or other elastomers; and

[0054] (11) Blends of thermoplastic rubbers with polyethylene,propylene, polyacetal, nylon, polyesters, cellulose esters, and thelike.

[0055] Preferably, the casing includes polymers, such as ethylene,propylene, butene-1 or hexane-1 based homopolymers or copolymersincluding functional monomers, such as acrylic and methacrylic acid andfully or partially neutralized ionomer resins and their blends, methylacrylate, methyl methacrylate homopolymers and copolymers, imidized,amino group containing polymers, polycarbonate, reinforced polyamides,polyphenylene oxide, high impact polystyrene, polyether ketone,polysulfone, poly(phenylene sulfide), acrylonitrile-butadiene,acrylic-styrene-acrylonitrile, poly(ethylene terephthalate),poly(butylene terephthalate), poly(ethelyne vinyl alcohol),poly(tetrafluoroethylene) and their copolymers including functionalcomonomers, and blends thereof. Suitable cover compositions also includea polyether or polyester thermoplastic urethane, a thermosetpolyurethane, a low modulus ionomer, such as acid-containing ethylenecopolymer ionomers, including E/X/Y terpolymers where E is ethylene, Xis an acrylate or methacrylate-based softening comonomer present inabout 0 to 50 weight percent and Y is acrylic or methacrylic acidpresent in about 5 to 35 weight percent. More preferably, in a low spinrate embodiment designed for maximum distance, the acrylic ormethacrylic acid is present in about 16 to 35 weight percent, making theionomer a high modulus ionomer. In a higher spin embodiment, the innercover layer includes an ionomer where an acid is present in about 10 to15 weight percent and includes a softening comonomer.

[0056] The cover preferably includes a polyurethane compositioncomprising the reaction product of at least one polyisocyanate, polyol,and at least one curing agent. Any polyisocyanate available to one ofordinary skill in the art is suitable for use according to theinvention. Exemplary polyisocyanates include, but are not limited to,4,4′-diphenylmethane diisocyanate (“MDI”); polymeric MDI;carbodiimide-modified liquid MDI; 4,4′-dicyclohexylmethane diisocyanate(“H₁₂ MDI”); p-phenylene diisocyanate (“PPDI”); m-phenylene diisocyanate(“MPDI”); toluene diisocyanate (“TDI”); 3,3′-dimethyl-4,4′-biphenylenediisocyanate (“TODI”); isophoronediisocyanate (“IPDI”); hexamethylenediisocyanate (“HDI”); naphthalene diisocyanate (“NDI”); xylenediisocyanate (“XDI”); p-tetramethylxylene diisocyanate (“p-TMXDI”);m-tetramethylxylene diisocyanate (“m-TMXDI”); ethylene diisocyanate;propylene-1,2-diisocyanate; tetramethylene-1,4-diisocyanate; cyclohexyldiisocyanate;1,6-hexamethylene-diisocyanate (“HDI”);dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,3-diisocyanate; cyclohexane-1,4- diisocyanate;1-isocyanato-3,3,5- trimethyl-5-isocyanatomethylcyclohexane; methylcyclohexylene diisocyanate; triisocyanate of HDI; triisocyanate of2,4,4-trimethyl-1,6-hexane diisocyanate (“TMDI”); tetracenediisocyanate; napthalene diisocyanate; anthracene diisocyanate;isocyanurate of toluene diisocyanate; uretdione of hexamethylenediisocyanate; and mixtures thereof. Polyisocyanates are known to thoseof ordinary skill in the art as having more than one isocyanate group,e.g., di-isocyanate, tri-isocyanate, and tetra-isocyanate. Preferably,the polyisocyanate includes MDI, PPDI, TDI, or a mixture thereof, andmore preferably, the polyisocyanate includes MDI. It should beunderstood that, as used herein, the term “MDI” includes4,4′-diphenylmethane diisocyanate, polymeric MDI, carbodiimide-modifiedliquid MDI, and mixtures thereof and, additionally, that thediisocyanate employed may be “low free monomer,” understood by one ofordinary skill in the art to have lower levels of “free” monomerisocyanate groups, typically less than about 0.1% free monomer groups.Examples of “low free monomer” diisocyanates include, but are notlimited to Low Free Monomer MDI, Low Free Monomer TDI, and Low FreeMonomer PPDI.

[0057] The at least one polyisocyanate should have less than about 14%unreacted NCO groups. Preferably, the at least one polyisocyanate has nogreater than about 7.5% NCO, and more preferably, less than about 7.0%.

[0058] Any polyol available to one of ordinary skill in the art issuitable for use according to the invention. Exemplary polyols include,but are not limited to, polyether polyols, hydroxy-terminatedpolybutadiene (including partially/fully hydrogenated derivatives),polyester polyols, polycaprolactone polyols, and polycarbonate polyols.In one preferred embodiment, the polyol includes polyether polyol.Examples include, but are not limited to, polytetramethylene etherglycol (“PTMEG”), polyethylene propylene glycol, polyoxypropyleneglycol, and mixtures thereof. The hydrocarbon chain can have saturatedor unsaturated bonds and substituted or unsubstituted aromatic andcyclic groups. Preferably, the polyol of the present invention includesPTMEG.

[0059] In another embodiment, polyester polyols are included in thepolyurethane material of the invention. Suitable polyester polyolsinclude, but are not limited to, polyethylene adipate glycol;polybutylene adipate glycol; polyethylene propylene adipate glycol;o-phthalate-1,6-hexanediol; poly(hexamethylene adipate) glycol; andmixtures thereof. The hydrocarbon chain can have saturated orunsaturated bonds, or substituted or unsubstituted aromatic and cyclicgroups.

[0060] In another embodiment, polycaprolactone polyols are included inthe materials of the invention. Suitable polycaprolactone polyolsinclude, but are not limited to, 1,6-hexanediol-initiatedpolycaprolactone, diethylene glycol initiated polycaprolactone,trimethylol propane initiated polycaprolactone, neopentyl glycolinitiated polycaprolactone, 1,4-butanediol-initiated polycaprolactone,and mixtures thereof. The hydrocarbon chain can have saturated orunsaturated bonds, or substituted or unsubstituted aromatic and cyclicgroups.

[0061] In yet another embodiment, the polycarbonate polyols are includedin the polyurethane material of the invention. Suitable polycarbonatesinclude, but are not limited to, polyphthalate carbonate andpoly(hexamethylene carbonate) glycol. The hydrocarbon chain can havesaturated or unsaturated bonds, or substituted or unsubstituted aromaticand cyclic groups. In one embodiment, the molecular weight of the polyolis from about 200 to about 4000.

[0062] Polyamine curatives are also suitable for use in the polyurethanecomposition of the invention and have been found to improve cut, shear,and impact resistance of the resultant balls. Preferred polyaminecuratives include, but are not limited to,3,5-dimethylthio-2,4-toluenediamine and isomers thereof;3,5-diethyltoluene-2,4-diamine and isomers thereof, such as3,5-diethyltoluene-2,6-diamine;4,4′-bis-(sec-butylamino)-diphenylmethane;1,4-bis-(sec-butylamino)-benzene, 4,4′-methylene-bis-(2-chloroaniline);4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) (“MCDEA”);polytetramethyleneoxide-di-p-aminobenzoate; N,N′-dialkyldiamino diphenylmethane; p,p′-methylene dianiline (“MDA”); m-phenylenediamine (“MPDA”);4,4′-methylene-bis-(2-chloroaniline) (“MOCA”);4,4′-methylene-bis-(2,6-diethylaniline) (“MDEA”);4,4′-methylene-bis-(2,3-dichloroaniline) (“MDCA”);4,4′-diamino-3,3′-diethyl-5,5′-dimethyl diphenylmethane; 2,2′,3,3′-tetrachloro diamino diphenylmethane; trimethylene glycoldi-p-aminobenzoate; and mixtures thereof. Preferably, the curing agentof the present invention includes 3,5-dimethylthio-2,4-toluenediamineand isomers thereof, such as ETHACURE 300, commercially available fromAlbermarle Corporation of Baton Rouge, La. Suitable polyamine curatives,which include both primary and secondary amines, preferably havemolecular weights ranging from about 64 to about 2000.

[0063] At least one of a diol, triol, tetraol, or hydroxy-terminatedcuratives may be added to the aforementioned polyurethane composition.Suitable diol, triol, and tetraol groups include ethylene glycol;diethylene glycol; polyethylene glycol; propylene glycol; polypropyleneglycol; lower molecular weight polytetramethylene ether glycol;1,3-bis(2-hydroxyethoxy) benzene; 1,3-bis-[2-(2-hydroxyethoxy) ethoxy]benzene; 1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy] ethoxy} benzene;1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol;resorcinol-di-(β-hydroxyethyl) ether; hydroquinone-di-(β-hydroxyethyl)ether; and mixtures thereof. Preferred hydroxy-terminated curativesinclude 1,3-bis(2-hydroxyethoxy) benzene; 1,3-bis-[2-(2-hydroxyethoxy)ethoxy] benzene; 1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy] ethoxy}benzene; 1,4-butanediol, and mixtures thereof. Preferably, thehydroxy-terminated curatives have molecular weights ranging from about48 to 2000. It should be understood that molecular weight, as usedherein, is the absolute weight average molecular weight and would beunderstood as such by one of ordinary skill in the art.

[0064] Both the hydroxy-terminated and amine curatives can include oneor more saturated, unsaturated, aromatic, and cyclic groups.Additionally, the hydroxy-terminated and amine curatives can include oneor more halogen groups. The polyurethane composition can be formed witha blend or mixture of curing agents. If desired, however, thepolyurethane composition may be formed with a single curing agent.

[0065] Any method known to one of ordinary skill in the art may be usedto combine the polyisocyanate, polyol, and curing agent of the presentinvention. One commonly employed method, known in the art as a one-shotmethod, involves concurrent mixing of the polyisocyanate, polyol, andcuring agent. This method results in a mixture that is inhomogenous(more random) and affords the manufacturer less control over themolecular structure of the resultant composition. A preferred method ofmixing is known as a prepolymer method. In this method, thepolyisocyanate and the polyol are mixed separately prior to addition ofthe curing agent. This method affords a more homogeneous mixtureresulting in a more consistent polymer composition. Other methodssuitable for forming the layers of the present invention includereaction injection molding (“RIM”), liquid injection molding (“LIM”),and pre-reacting the components to form an injection moldablethermoplastic polyurethane and then injection molding, all of which areknown to one of ordinary skill in the art.

[0066] An optional filler component may be chosen to impart additionaldensity to blends of the previously described components. The selectionof such filler(s) is dependent upon the type of golf ball desired (i.e.,one-piece, two-piece multi-component, or wound). Examples of usefulfillers include zinc oxide, barium sulfate, calcium oxide, calciumcarbonate and silica, as well as the other well known correspondingsalts and oxides thereof. Additives, such as nanoparticles, glassspheres, and various metals, such as titanium and tungsten, can be addedto the polyurethane compositions of the present invention, in amounts asneeded, for their well-known purposes. Additional components which canbe added to the polyurethane composition include UV stabilizers andother dyes, as well as optical brighteners and fluorescent pigments anddyes. Such additional ingredients may be added in any amounts that willachieve their desired purpose.

[0067] It has been found by the present invention that the use of acastable, reactive material, which is applied in a fluid form, makes itpossible to obtain very thin outer cover layers on golf balls.Specifically, it has been found that castable, reactive liquids, whichreact to form a urethane elastomer material, provide desirable very thinouter cover layers.

[0068] The castable, reactive liquid employed to form the urethaneelastomer material can be applied over the core using a variety ofapplication techniques such as spraying, dipping, spin coating, or flowcoating methods which are well known in the art. An example of asuitable coating technique is that which is disclosed in U.S. Pat. No.5,733,428, filed May 2, 1995 entitled “Method And Apparatus For FormingPolyurethane Cover On A Golf Ball,” the disclosure of which is herebyincorporated by reference in its entirety in the present application.

[0069] The cover is preferably formed around the casing by mixing andintroducing the material in the mold halves. It is important that theviscosity be measured over time, so that the subsequent steps of fillingeach mold half, introducing the core into one half and closing the moldcan be properly timed for accomplishing centering of the core coverhalves fusion and achieving overall uniformity. Suitable viscosity rangeof the curing urethane mix for introducing cores into the mold halves isdetermined to be approximately between about 2,000 cP and about 30,000cP, with the preferred range of about 8,000 cP to about 15,000 cP.

[0070] To start the cover formation, mixing of the prepolymer andcurative is accomplished in motorized mixer including mixing head byfeeding through lines metered amounts of curative and prepolymer. Toppreheated mold halves are filled and placed in fixture units usingcentering pins moving into holes in each mold. At a later time, a bottommold half or a series of bottom mold halves have similar mixture amountsintroduced into the cavity. After the reacting materials have resided intop mold halves for about 40 to about 80 seconds, a core is lowered at acontrolled speed into the gelling reacting mixture.

[0071] A ball cup holds the ball core through reduced pressure (orpartial vacuum). Upon location of the coated core in the halves of themold after gelling for about 40 to about 80 seconds, the vacuum isreleased allowing core to be released. The mold halves, with core andsolidified cover half thereon, are removed from the centering fixtureunit, inverted and mated with other mold halves which, at an appropriatetime earlier, have had a selected quantity of reacting polyurethaneprepolymer and curing agent introduced therein to commence gelling.

[0072] Similarly, U.S. Pat. No. 5,006,297 to Brown et al. and U.S. Pat.No. 5,334,673 to Wu both also disclose suitable molding techniques whichmay be utilized to apply the castable reactive liquids employed in thepresent invention. Further, U.S. Pat. Nos. 6,180,040 and 6,180,722disclose methods of preparing dual core golf balls. The disclosures ofthese patents are hereby incorporated by reference in their entirety.However, the method of the invention is not limited to the use of thesetechniques.

[0073] Depending on the desired properties, balls prepared according tothe invention can exhibit substantially the same or higher resilience,or coefficient of restitution (“COR”), with a decrease in compression ormodulus, compared to balls of conventional construction. Additionally,balls prepared according to the invention can also exhibit substantiallyhigher resilience, or COR, without an increase in compression, comparedto balls of conventional construction. Another measure of thisresilience is the “loss tangent,” or tan 6, which is obtained whenmeasuring the dynamic stiffness of an object. Loss tangent andterminology relating to such dynamic properties is typically describedaccording to ASTM D4092-90. Thus, a lower loss tangent indicates ahigher resiliency, thereby indicating a higher rebound capacity. Lowloss tangent indicates that most of the energy imparted to a golf ballfrom the club is converted to dynamic energy, i.e., launch velocity andresulting longer distance. The rigidity or compressive stiffness of agolf ball may be measured, for example, by the dynamic stiffness. Ahigher dynamic stiffness indicates a higher compressive stiffness. Toproduce golf balls having a desirable compressive stiffness, the dynamicstiffness of the crosslinked reaction product material should be lessthan about 50,000 N/m at −50° C. Preferably, the dynamic stiffnessshould be between about 10,000 and 40,000 N/m at −50° C., morepreferably, the dynamic stiffness should be between about 20,000 and30,000 N/m at −50° C.

[0074] The molding process and composition of golf ball portionstypically results in a gradient of material properties. Methods employedin the prior art generally exploit hardness to quantify these gradients.Hardness is a qualitative measure of static modulus and does notrepresent the modulus of the material at the deformation ratesassociated with golf ball use, i.e., impact by a club. As is well knownto one skilled in the art of polymer science, the time-temperaturesuperposition principle may be used to emulate alternative deformationrates. For golf ball portions including polybutadiene, a 1-Hzoscillation at temperatures between 0° C. and −50° C. are believed to bequalitatively equivalent to golf ball impact rates. Therefore,measurement of loss tangent and dynamic stiffness at 0° C. to −50° C.may be used to accurately anticipate golf ball performance, preferablyat temperatures between about −20° C. and −50° C.

[0075] The resultant golf balls typically have a coefficient ofrestitution of greater than about 0.7, preferably greater than about0.75, and more preferably greater than about 0.78. The golf balls alsotypically have an Atti compression of at least about 40, preferably fromabout 50 to 120, and more preferably from about 60 to 100. The golf ballcured polybutadiene material typically has a hardness of at least about15 Shore A, preferably between about 30 Shore A and 80 Shore D, morepreferably between about 50 Shore A and 60 Shore D.

[0076] The core composition should comprise at least one rubber materialhaving a resilience index of at least about 40. Preferably theresilience index is at least about 50. Polymers that produce resilientgolf balls and, therefore, are suitable for the present invention,include but are not limited to CB23, CB22, commercially available fromof Bayer Corp. of Orange, Tex., BR60, commercially available fromEnichem of Italy, and 1207G, commercially available from Goodyear Corp.of Akron, Ohio. To clarify the method of computation for resilienceindex, the resilience index for CB23, for example, is computed asfollows:

Resilience Index for CB23=100,000·[(0.954)−(0.407)]/990 Resilience Indexfor CB23=55

[0077] Additionally, the unvulcanized rubber, such as polybutadiene, ingolf balls prepared according to the invention typically has a Mooneyviscosity of between about 40 and about 80, more preferably, betweenabout 45 and about 65, and most preferably, between about 45 and about55. Mooney viscosity is typically measured according to ASTM-D1646.

[0078] When golf balls are prepared according to the invention, theytypically will have dimple coverage greater than about 60 percent,preferably greater than about 65 percent, and more preferably greaterthan about 75 percent. The flexural modulus of the cover on the golfballs, as measured by ASTM method D6272-98, Procedure B, is typicallygreater than about 500 psi, and is preferably from about 500 psi to150,000 psi. As discussed herein, the outer cover layer is preferablyformed from a relatively soft polyurethane material. In particular, thematerial of the outer cover layer should have a material hardness, asmeasured by ASTM-D2240, less than about 45 Shore D, preferably less thanabout 40 Shore D, more preferably between about 25 and about 40 Shore D,and most preferably between about 30 and about 40 Shore D. The casingpreferably has a material hardness of less than about 70 Shore D, morepreferably between about 30 and about 70 Shore D, and most preferably,between about 50 and about 65 Shore D.

[0079] In a preferred embodiment, the casing material hardness isbetween about 40 and about 70 Shore D and the outer cover layer materialhardness is less than about 40 Shore D. In a more preferred embodiment,a ratio of the casing material hardness to the outer cover layermaterial hardness is greater than 1.5.

[0080] It should be understood, especially to one of ordinary skill inthe art, that there is a fundamental difference between “materialhardness” and “hardness, as measured directly on a golf ball.” Materialhardness is defined by the procedure set forth in ASTM-D2240 andgenerally involves measuring the hardness of a flat “slab” or “button”formed of the material of which the hardness is to be measured.Hardness, when measured directly on a golf ball (or other sphericalsurface) is a completely different measurement and, therefore, resultsin a different hardness value. This difference results from a number offactors including, but not limited to, ball construction (i.e., coretype, number of core and/or cover layers, etc.), ball (or sphere)diameter, and the material composition of adjacent layers. It shouldalso be understood that the two measurement techniques are not linearlyrelated and, therefore, one hardness value cannot easily be correlatedto the other.

[0081] The core of the present invention has an Atti compression ofbetween about 50 and about 90, more preferably, between about 60 andabout 85, and most preferably, between about 65 and about 85. Theoverall outer diameter (“OD”) of the core is less than about 1.590inches, preferably, no greater than 1.580 inches, more preferablybetween about 1.540 inches and about 1.580 inches, and most preferablybetween about 1.525 inches to about 1.570 inches. The OD of the casingof the golf balls of the present invention is preferably between 1.580inches and about 1.640 inches, more preferably between about 1.590inches to about 1.630 inches, and most preferably between about 1.600inches to about 1.630 inches.

[0082] The present multilayer golf ball can have an overall diameter ofany size. Although the United States Golf Association (“USGA”)specifications limit the minimum size of a competition golf ball to1.680 inches. There is no specification as to the maximum diameter. Golfballs of any size, however, can be used for recreational play. Thepreferred diameter of the present golf balls is from about 1.680 inchesto about 1.800 inches. The more preferred diameter is from about 1.680inches to about 1.760 inches. The most preferred diameter is about 1.680inches to about 1.740 inches.

[0083] The golf balls of the present invention should have a moment ofinertia (“MOI”) of less than about 85 and, preferably, less than about83. The MOI is typically measured on model number MOI-005-104 Moment ofInertia Instrument manufactured by Inertia Dynamics of Collinsville,Conn. The instrument is plugged into a PC for communication via a COMMport and is driven by MOI Instrument Software version #1.2.

EXAMPLE

[0084] Golf balls were prepared, both according to the present inventionand conventional technology, and are formed of a solid core having adiameter of 1.550 inches, a casing having a thickness of 0.035 inches,and an outer cover layer having a thickness of 0.030 inches, to providea golf ball outer diameter of 1.68 inches. Two examples of golf ballsaccording to the present invention were prepared, each having adifferent cover hardness. Example I, having a cover material hardness of38 Shore D, and Example II, having a cover material hardness of 30 ShoreD, are presented below in Table I. The outer cover of the Control golfball, prepared according to conventional technology, comprises a PMS1088prepolymer, commercially available from Polyurethane Specialties Co.(77.8%) cured with Ethacure 300, commercially available from AlbemarleCorp. (18.7%), and white dispersion, commercially available from HarwichChemical (3.5%). TABLE I Composition Control Example I Example IIMDI/PTMEG 2000 — 6.0% NCO 6.0% NCO prepolymer PMS1088 prepolymer 6.0%NCO Versalink P-250¹ — 0.270 eq. 0.550 eq. Versalink P-650² — — —Ethacure 300³ 0.95 eq. 0.680 eq. 0.400 eq. HCC-19584 White 3.5% 3.5%3.5% Dispersion⁴ Dabco-33LV Catalyst⁵ — — 0.100% Properties Materialhardness (Shore D) 45 38 30

[0085] The casing layer for Examples I and II, and for the Control ball,were formed of a 50/50 Na/Li blend of SURLYN® 8945 and SURLYN® 7940.

[0086] Examples I and II were tested for a variety of golf ballproperties, such as core compression, cover hardness, ball compression,ball velocity, ball moment of inertia, ball COR, and driver, 8-iron,½-wedge, and full wedge spin, and compared to the Control ball, alsotested for the same properties. The results for Examples I and II, andthe Control ball, are presented below in Table II. TABLE II BallProperties Control Example I Example II Core compression (Atti) 73 76 86Core diameter (inches) 1.550 1.550 1.550 Casing thickness (inches) 0.0350.035 0.035 Casing diameter (inches) 1.620 1.620 1.620 Casing materialNa/Li blend Na/Li blend Na/Li blend Cover hardness (Shore D) material 4530 38 on ball 55 54 54 Ball compression (Atti) 85 84 91 Ball velocity(ft/s) 253.2 254.6 255.1 Ball Moment of Inertia 81.1 81.4 — (g · cm²)Ball COR 0.808 0.816 0.822 Spin Standard Driver spin (rpm) 3370 34603580 8-iron spin (rpm) 7430 7780 7930 ½-wedge spin (rpm) 6930 7040 7200full-wedge spin (rpm) 9400 9620 9840

[0087] It is clear from the data presented in Table II, that the golfballs of the present invention have increased 8-iron spin, ½-wedge, andfull wedge, all of which are important to making approach shots stop atdesired locations on the green, especially to those golfers whose launchconditions require a ball having higher iron spin.

[0088] The invention described and claimed herein is not to be limitedin scope by the specific embodiments herein disclosed, since theseembodiments are intended as illustrations of several aspects of theinvention. Any equivalent embodiments are intended to be within thescope of this invention. Indeed, various modifications of the inventionin addition to those shown and described herein will become apparent tothose skilled in the art from the foregoing description. Suchmodifications are also intended to fall within the scope of the appendedclaims.

What is claimed is:
 1. A golf ball comprising a solid core, an outercover layer, and a casing disposed between the core and the outer coverlayer, wherein: the core has an outer diameter of no greater than about1.58 inches; the casing has an outer diameter of greater than 1.58inches and a material hardness of between about 30 and about 70 Shore D;and the outer cover layer has a material hardness of less than about 45Shore D.
 2. The golf ball of claim 1, wherein the outer cover layermaterial hardness is less than about 40 Shore D.
 3. The golf ball ofclaim 2, wherein the outer cover layer material hardness is betweenabout 25 and about 40 Shore D.
 4. The golf ball of claim 1, wherein thecasing material hardness is between about 50 and about 65 Shore D. 5.The golf ball of claim 1, wherein at least one of the casing and theouter cover layer has a thickness of less than about 0.05 inches.
 6. Thegolf ball of claim 5, wherein at least one of the casing and the outercover layer has a thickness of between about 0.02 inches and about 0.04inches.
 7. The golf ball of claim 1, wherein the casing outer diameteris from 1.58 inches to about 1.64 inches.
 8. The golf ball of claim 7,wherein the casing outer diameter is from about 1.59 inches to about1.63 inches.
 9. The golf ball of claim 1, wherein the outer cover layeris formed of a polyurethane composition comprising the reaction productof at least one polyisocyanate, a polyol, and at least one curing agent.10. The golf ball of claim 1, wherein the ball has a moment of inertiaof less than about 85 g.cm².
 11. The golf ball of claim 10, wherein theball has a moment of inertia of less than about 83 g.cm².
 12. The golfball of claim 1, wherein the core has a first hardness and the casinghas a second hardness greater than the first.
 13. The golf ball of claim12, wherein the outer cover layer has a third hardness less than thesecond hardness.
 14. The golf ball of claim 1, wherein the casingcomprises ionic copolymers of ethylene and an unsaturated monocarboxylicacid; vinyl resins; polyolefins; polyurethanes; polyureas; polyamides;thermoplastic and thermoset resins; metallocenes; acrylic resins;thermoplastic polyesters; and mixtures thereof.
 15. The golf ball ofclaim 14, wherein the casing comprises comprises ionic copolymers ofethylene and an unsaturated monocarboxylic acid.
 16. The golf ball ofclaim 1, wherein the casing material hardness is between about 40 andabout 70 Shore D and the outer cover layer material hardness is lessthan about 40 Shore D.
 17. The golf ball of claim 1, wherein a ratio ofthe casing material hardness to the outer cover layer material hardnessis greater than 1.5.
 18. The golf ball of claim 1, wherein the corecomprises a cis-to-trans catalyst.
 19. The golf ball of claim 1, whereinat least one of the core, casing, and cover layer are cast, reactioninjection molded, liquid injection molded, injection molded, or amixture thereof.